自动编译在 Eclipse-maven-Scala 项目中不起作用

Question

我正在处理我在 Eclipse 中创建的 scala 项目。当我更改 scala 文件时，它没有反映它说“错误：无法找到或加载主类 com.sparkscala.MainExample”，但是当我构建它时，它可以成功运行。

pom.xml 配置：

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.spark-scala</groupId>
    <artifactId>spark-scala</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>${project.artifactId}</name>
    <description>Spark in Scala</description>
    <inceptionYear>2010</inceptionYear>

    <properties>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
        <encoding>UTF-8</encoding>
        <scala.tools.version>2.10</scala.tools.version>
        <!-- Put the Scala version of the cluster -->
        <scala.version>2.10.4</scala.version>
    </properties>

    <!-- repository to add org.apache.spark -->
    <repositories>
        <repository>
            <id>cloudera-repo-releases</id>
            <url>https://repository.cloudera.com/artifactory/repo/</url>
        </repository>
    </repositories>

    <build>
        <sourceDirectory>src/main/scala</sourceDirectory>
        <testSourceDirectory>src/test/scala</testSourceDirectory>
        <plugins>
            <plugin>
                <!-- see http://davidb.github.com/scala-maven-plugin -->
                <groupId>net.alchim31.maven</groupId>
                <artifactId>scala-maven-plugin</artifactId>
                <version>3.2.1</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>compile</goal>
                            <goal>testCompile</goal>
                        </goals>
                        <configuration>
                            <args>
                                <arg>-make:transitive</arg>
                                <arg>-dependencyfile</arg>
                                <arg>${project.build.directory}/.scala_dependencies</arg>
                            </args>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>2.13</version>
                <configuration>
                    <useFile>false</useFile>
                    <disableXmlReport>true</disableXmlReport>
                    <includes>
                        <include>**/*Test.*</include>
                        <include>**/*Suite.*</include>
                    </includes>
                </configuration>
            </plugin>

            <!-- "package" command plugin -->
            <plugin>
                <artifactId>maven-assembly-plugin</artifactId>
                <version>2.4.1</version>
                <configuration>
                    <descriptorRefs>
                        <descriptorRef>jar-with-dependencies</descriptorRef>
                    </descriptorRefs>
                </configuration>
                <executions>
                    <execution>
                        <id>make-assembly</id>
                        <phase>package</phase>
                        <goals>
                            <goal>single</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.scala-tools</groupId>
                <artifactId>maven-scala-plugin</artifactId>
                <executions>
                    <execution>
                        <id>scala-compile-first</id>
                        <phase>process-resources</phase>
                        <goals>
                            <goal>add-source</goal>
                            <goal>compile</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>scala-test-compile</id>
                        <phase>process-test-resources</phase>
                        <goals>
                            <goal>testCompile</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

    <dependencies>
        <!-- Scala and Spark dependencies -->
        <dependency>
            <groupId>org.scala-lang</groupId>
            <artifactId>scala-library</artifactId>
            <version>${scala.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-core_2.10</artifactId>
            <version>1.2.0-cdh5.3.1</version>
        </dependency>

    </dependencies>
</project>

Answer 1

这很复杂
Scala 编译器缓慢而令人毛骨悚然。它会运行最后一个编译好的文件，而不是清楚地告诉你麻烦。因此，如果您正在执行 println("Hello World")，请尝试更改为“Hello Something Else”，以查看是否真的有编译正在进行，或者 IDE 只是选择了最后一个好的编译文件。
加上你的 pom.xml 不正确。 我建议去 Eclipse 的 Windows -> Show View -> Problems.. 你肯定有一些问题。首先删除它们。清理、构建并再次运行。
如果要使用 Spark，则必须确保 Scala 版本与 Eclipse 项目构建路径中的版本匹配。 这是一个很好的 pom.xml，它具有正确版本的 Spark 作为唯一依赖项。无需添加 Scala 库依赖项，因为它已包含在 Spark 依赖项层次结构中。另外，确保 Eclipse 项目构建路径中的 Scala 库版本与我在 pom.xml 中提供的版本匹配，即 2.11.x >>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.spark-scala</groupId>
    <artifactId>spark-scala</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>${project.artifactId}</name>
    <description>Spark in Scala</description>
    <inceptionYear>2010</inceptionYear>

    <properties>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
        <encoding>UTF-8</encoding>
        <scala.tools.version>2.10</scala.tools.version>
        <!-- Put the Scala version of the cluster -->
        <scala.version>2.10.4</scala.version>
    </properties>

    <!-- repository to add org.apache.spark -->
    <repositories>
        <repository>
            <id>cloudera-repo-releases</id>
            <url>https://repository.cloudera.com/artifactory/repo/</url>
        </repository>
    </repositories>

    <build>
        <sourceDirectory>src/main/scala</sourceDirectory>
        <testSourceDirectory>src/test/scala</testSourceDirectory>
        <plugins>
            <plugin>
                <!-- see http://davidb.github.com/scala-maven-plugin -->
                <groupId>net.alchim31.maven</groupId>
                <artifactId>scala-maven-plugin</artifactId>
                <version>3.2.1</version>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>2.13</version>
                <configuration>
                    <useFile>false</useFile>
                    <disableXmlReport>true</disableXmlReport>
                    <includes>
                        <include>**/*Test.*</include>
                        <include>**/*Suite.*</include>
                    </includes>
                </configuration>
            </plugin>

            <!-- "package" command plugin -->
            <plugin>
                <artifactId>maven-assembly-plugin</artifactId>
                <version>2.4.1</version>
                <configuration>
                    <descriptorRefs>
                        <descriptorRef>jar-with-dependencies</descriptorRef>
                    </descriptorRefs>
                </configuration>
                <executions>
                    <execution>
                        <id>make-assembly</id>
                        <phase>package</phase>
                        <goals>
                            <goal>single</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.scala-tools</groupId>
                <artifactId>maven-scala-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

    <dependencies>
        <dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-core_2.11</artifactId>
            <version>1.2.1</version>
        </dependency>
    </dependencies>
</project>